1. Field of the Invention
The present invention relates generally to improvements in the design and operation of article handling apparatus and is particularly useful in the environment of article handling devices that use a suction-type article handling mechanism.
2. Description of the Prior Art
Most prior art article handling mechanisms, more specifically referred to in the description of the present invention as being in the environment of a point-of-sale (POS) article dispenser, rely on a multitude of motors, switches and solenoids for moving various portions of the handling mechanism, and handling of the articles themselves, such as packaged products. Most such machines require one motor, switch and/or solenoid dedicated for each row, column or type of article or package to be handled or dispensed therefrom. Such machines generally suffer from numerous disadvantages, such as poor reliability due to mechanical failures, as well known by those skilled in this art.
U.S. Pat. No. 5,240,139 represents a significant improvement in article handling devices. It describes the use of a negative air pressure lifter (i.e., article pickup or handling mechanism), which uses suction, i.e., a reduced or so-called xe2x80x9cnegativexe2x80x9d air pressure created by a partial vacuum, for making a secure contact to an article to be retrieved by entering the open top of an article storage bin located in a refrigerated storage area of a vending machine. Although robotic, and specifically suction-type lifting mechanisms are in common use in factory settings, where space limitations are generally relaxed, their use in tight confines, such as an article vending machine, has not gained wide acceptance. Due to the greater reliability and versatility of vending machines of the type which utilizes suction technology for grasping and moving selected articles, it would be desirable to develop new techniques and methods for the operation and control of such machines, as well as for other more generalized article handling mechanisms.
Article contact detection is provided in the forenoted U.S. Pat. No. 5,240,139 by a mechanical or electromechanical proximity switch mounted at the article pickup end of the negative air pressure lifter.
It would be desirable to avoid the use of a proximity switch type of sensor at the article pickup end of the lifter, most notably because of the necessity of providing to the pickup head power and signal carrying conductors associated with the switch. Such conductors not only present obstacles to the freedom of movement of the pickup head, but also present reliability problems due totheir potential for breakage. However, even if a xe2x80x9cremotely-positionedxe2x80x9d typeof product contact sensor is provided, care must be taken to ensure that it is simple and reliable.
Furthermore, a vacuum breaker would also be desirable in a vending machine having a suction-type article handler, in order to facilitate a xe2x80x9cquick releasexe2x80x9d of the product at the end of the dispensing cycle. U.S. Pat. No. 5,957,326 entitled APPARATUS FOR RETRIEVING RANDOMLY ORGANIZED ARTICLES, describes a vending apparatus having a suction-type article handler and a vacuum breaker. A pickup head having a plurality of suction cups mounted thereon (in order to help ensure the retrieval of one of a plurality of randomly organized articles for a storage bin) is lowered into thestorage bin as suction is applied to the cups. Afterthe passage of a predeterminedamount of time, the machine controller causes the pickup head to start being removed from the bin. While the pickup head is being removed, a vacuum sensing assembly coupled to each suction cup determines if more than one of the suction cups has an article attachedthereto (i.e., article contact is assumed in response to the sensing of vacuum in the hose coupled to a given suction cup). If more than one suction cup has an article adhered thereto, the machine controller causes a release of vacuum from all of the suction cups except one.
PCT patent publication WO 99/12132 entitled VENDING MACHINE discloses a vending machine having an articulated arm for positioning an article gripping suction hose into a freezer for retrieving articles to be dispensed. It teaches the use of both an electromechanically operated proximity switch at thearticle gripper head for turning the vacuum source on when the gripper makes contact with the product, as well as the use of a position sensor for advising the machine controller to energize a vacuum breaker when the gripperhead reaches a predetermined position indicative of the product reaching the dispensing area.
Accordingly, one of the objects of the present invention is to provide new techniques and methods for the design, operation and control of article handling mechanisms.
It is a further object of the present invention to provide new techniques and methods for the design, operation and control of article handling mechanisms of the type that utilize computer-controlled electromechanical technology, and in the illustrated embodiment a robotically positioned suction-type gripper, for grasping and moving a selected article from one area to another, such as from a storage area to a dispensing area.
It is also an object of the present invention to provide new techniques and methods for such mechanisms, which improve the speed and accuracy of the article handling operation while still handling the articles to be dispensed in a careful manner so as to prevent any damage thereto.
The above objects are achieved in an illustrated embodiment of an article dispensing apparatus embodied, for example, as a vending machine, including a controllably positioned suction hose dispenser for retrieving articles from a storage area. In one embodiment, a sensor having an output responsive to changes in partial pressure inside the air hose, such as an airflow sensor coupled to the suction-hose, can initially act to sense the timing of contact of the suction hose with an article to be dispensed. As long as suction is provided to the gripping end of the suction hose prior to the hose contacting the article to be retrieved, the airflow (and partial pressure) inside the hose will change dramatically as the gripping end of the suction hose makes contact with the article. Furthermore, at the moment when the gripping end of the suction hose is no longer in substantial contact with the article, the airflow sensor again provides an indication signal, due to the sudden change in airflow (and partial pressure) that occurs at the time within the hose. The signals generated by the airflow sensor can be used in place of the prior art mechanically operated proximity sensor, to stop the approach of the gripping end of the hose towards the article, and serve as an indication to initiate removal of the article from the storage area.
When the control mechanism of the dispenser has determined normal operation, the time of the occurrence of the airflow signal can be used by the control mechanism to confirm that the article has been properly moved, for example from the storage area to a dispensing area, but if the sensed airflow signal has been determined by the control mechanism to be premature (because the signal from the airflow sensor occurred before the hose positioner moved the hose to a predetermined dispensing position), it""s occurrence indicates a faulty or failed dispensing/vend operation. Accordingly, the control mechanism can then take appropriate action, such as to re-attempt the dispensing operation.
When the airflow signal indicates proper operation, the control mechanism can also use the airflow signal for checking, and recalibrating if necessary, it""s control of the hose positioner.
In an embodiment illustrated herein, the airflow sensor is used in combination with an airflow control mechanism, i.e., a vacuum or suction release (i.e., breaker), to facilitate a xe2x80x9cquick-releasexe2x80x9d of the article being handled. In this regard, the airflow sensor can be included in its own housing, or as in the illustrated embodiment, a housing which also includes therein the vacuum release/breaker mechanism. Furthermore, a mechanical or electro-mechanical linkage can be used to activate the breaker in response to mechanical contact by the article handling mechanism, and thereby cause a rapid equalization of air pressure inside the housing towards ambient when it is time for the article handling mechanism to release the selected article. Even furthermore, since contact of the article handling mechanism with the mechanical or electro-mechanical linkage occurs at a known position, the known position can signify a xe2x80x9cvirtual homexe2x80x9d and therefore reaching this xe2x80x9cvirtual homexe2x80x9d position can be used by the control mechanism, as noted above, to check the accuracy of it""spositioning control of the article handling mechanism, and if necessary, its recalibration. In a further embodiment, position sensing for the article handling mechanism and activation of the breaker could be carried out using equivalent electro-mechanical or all electronic devices, such as a magnetically operated position switch, or a solenoid, respectively.
Although use of an airflow sensor is described in the preferred embodiment, it is intended that a vacuum sensor coupled to the hose so to sense changes in the partial pressure inside the hose, is a further embodiment in place of, or even in addition to, the described airflow sensor. However, some of the advantages of an airflow sensor in the present embodiment are that it has more tolerance and is more accepting of power and vacuum fluctuations. Rather than determining vacuum at a present level, which may require a more delicate measuring apparatus, the airflow sensor more easily determines changes in relatively small amounts of airflow in the hose.